Many vehicles employ driver and passenger airbags as safety features of a vehicle vehicles. When an airbag is deployed a door defined in the airbag cover has to open to allow inflation of the airbag. Typically the door is formed by lines of weakness in the airbag cover, with the lines of weakness typically being arranged to create controlled movement of the door.
In one design of passenger airbag the cover includes a door which is arranged to be deployed by opening about one of its edges in a hinged arrangement before the hinged edge is torn from the rest of the cover. However problems may arise if the airbag door movement is not controlled.
It has therefore been proposed to provide a flexible tether extending between a fixed anchor point and the airbag door to prevent the airbag door from departing in an uncontrolled manner from the airbag cover. However the forces applied on the airbag door are very high and typically such tethers will eventually tear. However the tether can serve to absorb some of the energy of the door.
Tethers have been designed which attempt to control the movement of a door. One such example is described in U.S. Pat. No. 5,308,111. In this arrangement a single strap extends from one side of the airbag door across the airbag to the other edge of the airbag door thus serving as two tethers tethering opposite edges of the airbag door. The strap extending between the edge of the airbag door and fixed anchor points is folded several times where the folds are non-parallel to one another.
In the specification the term `fixed anchor point` is intended to encompass any member within the vehicle which will remain substantially fixed during airbag deployment and which is strong enough to withstand the forces applied to the airbag door to allow the door to be tethered to it. Typically this will comprise a bracket on the airbag mechanism or part of the instrument panel.